Replace System.Drawing.Common

[siriak]

We need to replace System.Drawing.Common with something else because it's Windows-only since version 6.

I propose to use SkiaSharp instead. It's one of the alternatives to System.Drawing.Common Microsoft recommends here. Compared to other alternatives, it looks more popular and better maintained.

I'm not familiar with the interface SkiaSharp provides, but I assume it's different from what System.Drawing.Common has. Nevertheless, we use only the most basic drawing features in the repository, so it should be not too difficult to migrate.

This update is a part of #425.

[siriak]

@gmottajr will you be able to do the upgrade?

[gmottajr]

Sounds good, @siriak!
Let's work on it.

[siriak]

@gmottajr, how are you doing? Do you still plan to implement this or it can be grabbed by somebody else?

[siriak]

This is completed